Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C09J133/08—Homopolymers or copolymers of acrylic acid esters
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C09J133/10—Homopolymers or copolymers of methacrylic acid esters
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C09J133/062—Copolymers with monomers not covered by C09J133/06
  • C09J133/064—Copolymers with monomers not covered by C09J133/06 containing anhydride, COOH or COOM groups, with M being metal or onium-cation
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C09J133/062—Copolymers with monomers not covered by C09J133/06
  • C09J133/068—Copolymers with monomers not covered by C09J133/06 containing glycidyl groups
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
  • C09J4/06—Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
  • C09J7/38—Pressure-sensitive adhesives [PSA]
  • C09J7/381—Pressure-sensitive adhesives [PSA] based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
  • C09J7/385—Acrylic polymers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J9/00—Adhesives characterised by their physical nature or the effects produced, e.g. glue sticks
  • C09J9/02—Electrically-conducting adhesives
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2301/00—Additional features of adhesives in the form of films or foils
  • C09J2301/30—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier
  • C09J2301/302—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier the adhesive being pressure-sensitive, i.e. tacky at temperatures inferior to 30°C

Definitions

• the present invention relates to a thermally curable, high temperature resistant, (semi-)structural pressure-sensitive adhesive composition, an electrically conductive adhesive composition, adhesive tapes made therefrom and the use thereof.
• the pressure-sensitive adhesives or electrically conductive adhesives can be used for electronic and electrical products, automobile products and new energy equipment (such as solar energy and wind energy equipment).
• Polyacrylate pressure-sensitive adhesives are a class of adhesive products with a very broad range of applications. Pressure-sensitive adhesives commonly used in industries are normally made by copolymerization of isooctyl methacrylate (I OA) or 2-ethylhexyl methacrylate (2-EHA) and other monomers. These pressure-sensitive adhesives have ideal peel strength on most of bonded surfaces, therefore, have extremely high bonding efficiencies. However, a critical disadvantage of the pressure- sensitive adhesives is their weak bonding strength (shear strength is normally no greater than 1 MPa), and therefore the pressure-sensitive adhesives is not suitable for small area bonding. Meanwhile, polyacrylate pressure-sensitive adhesives normally don't have good temperature resistance. These pressure-sensitive adhesives will gradually degrade at high temperatures causing their strength to decrease.
• Polyoxazine resin is a new type of phenolic resin, having overcome the disadvantage of releasing small molecules during forming and curing process of conventional phenolic resins. Therefore, the polyoxazine resin has attracted wide attention of researchers in the aspect of producing high performance materials. However, the polyoxazine resin also has some disadvantages, such as high brittleness, high curing temperature and difficulty in film-forming.
• WO2003/072638 discloses a curable composition comprising benzoxazine compounds or resins and at least one other curable unsaturated compounds or resins.
• the composition can further comprise a curing agent or other filling agents.
• Such compositions can be used as adhesives, coatings and sealants.
• pressure-sensitive adhesive compositions comprising specifically designed polyacrylate and oxazine can overcome the existing problems of storage stability at ambient
• the present invention provides a thermally curable pressure-sensitive adhesive
• composition and, based on the total weight of the composition, the composition comprises the following components:
• X is selected from the group consisting of a covalent bond, Ci-Ce alkylene, C3-C10 cycloalkylene
• Ri and R 2 are the same or different and independently of each other selected from the group consisting of hydrogen, Ci-Ce alkyl, or C5-Q4 aryl, and
• R4 is selected from the group consisting of hydrogen, halogen or Ci-Ce alkyl.
• Another aspect of the present invention provides an electrically conductive adhesive
• composition comprising the above-described thermally curable pressure-sensitive adhesive composition, and an electrically conductive material.
• Yet another aspect of the present invention provides an adhesive tape, comprising the above- described thermally curable pressure-sensitive adhesive composition, or an electrically conductive adhesive composition, and a base material.
• the present invention also provides for the use of the thermally curable pressure-sensitive adhesive composition or the electrically conductive adhesive composition in preparing membranes used for electronic and electrical products, automobile products and new energy equipment.
• the thermally curable pressure-sensitive adhesive composition and the electrically conductive adhesive composition of the present invention are high temperature resistant, pressure-sensitive,
• compositions of the present invention which have preserved advantages of convenience and effectiveness in the use of ordinary pressure-sensitive adhesive tapes, and can achieve (semi-)structural strength after being thermally cured. Moreover, the compositions of the present invention have excellent long-term (as long as over 12 months at room temperature) storage stability at room temperature.
• Figure 1 shows rheological curves of elastic modulus (G') of the reactive
• structural adhesive refers to an adhesive with shear strength of greater than 1,000 psi (1 MPa is equivalent to about 145 psi).
• structural strength refers to shear strength of greater than 1 ,000 psi.
• shear strength refers to shear strength of greater than 100 psi, but less than 1,000 psi.
• the "(semi-)structural adhesive” as described herein can be semi-cured (i.e., incompletely cured), but can achieve semi-structural strength (i.e., structural strength of a semi-structural adhesive) and can meet requirements for the use although being incompletely cured. Such an incompletely cured semi- structural adhesive and the materials to be bound can still be further cured to achieve a higher strength if they are further heated to a certain temperature under practical work conditions.
• methacrylate refers to acrylate and/or methacrylate.
• alkyl refers to a saturated, straight-chain or branched, non-cyclic hydrocarbon having from 1 to 10 carbon atoms, preferably from 1 to 6 carbon atoms, and more preferably from 1 to 4 carbon atoms.
• Representative straight-chain alkyls include methyl, ethyl, n- propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl and n-decyl; while representative branched alkyls include isopropyl, sec -butyl, isobutyl, tert-butyl, isopentyl, 2-methylbutyl, 3-methylbutyl, 2- methylpentyl, 3-methylpentyl, 4-methylpentyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 5- methylhexyl, 2,3-dimethylbutyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, 2,3-dimethylhexyl, 2,4- dimethylhexyl, 2,5-dimethylhexyl, 2,2-d
• Ci-Ce alkyl refers to a straight-chain or branched alkyl having from 1 to 6 carbon atoms, e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and the like.
• d- alkylene refers to a straight-chain or branched alkylene having from 1 to 6 carbon atoms, e.g., methylene (-CH 2 -), ethylene (-CH 2 CH ), trimethylene (-CH 2 CH 2 CH 2 -), -CH 2 -CH(CH 3 )-, -C(CH 3 ) 2 -, tetramethylene (-CH 2 CH 2 CH 2 CH 2 -, -CH 2 -CH 2 -CH(CH 3 )-, -CH 2 -CH(CH 3 )-CH 2 -, etc., and the like.
• C 3 -Ci 0 cycloalkylene group refers to a saturated hydrocarbon radical having two free valences and at least one ring that may be bridged or fused. Representative examples include cyclopentylene, cyclohexylene, cycloheptylene, cyclooctylene, and the like.
• halogen includes fluorine, chlorine, bromine or iodine; preferably fluorine, chlorine or bromine; and more preferably chlorine or bromine.
• C5-C14 aryl includes aromatic hydrocarbon groups that may be saturated or unsaturated, fused or bridged.
• the present invention provides a thermally curable pressure-sensitive adhesive composition and, based on total weight of the composition, the composition comprises the following components:
• Ri and R 2 are the same or different and independently of each other selected from the group consisting of hydrogen, Ci-C 6 alkyl, or C5-Q4 aryl, and
• R 4 is selected from the group consisting of hydrogen, halogen or Ci-C 6 alkyl.
• the benzoxazine is present in an amount of 5-40% by weight, preferably 18-30% by weight, based on the total weight of the composition.
• the reactive polymethacrylate component is present in an amount of 60-95% by weight, based on the total weight of the composition.
• the reactive polymethacrylate component is present in an amount of 70-82% by weight, based on the total weight of the composition.
• the reactive functional group is selected from at least one of the group consisting of epoxy group, carboxyl group and hydroxyl group.
• the reactive polymethacrylate is formed by polymerization of one or more monomers selected from the following monomers:
• a3) optionally, methacrylic acid and/or methacrylamide.
• the monomer of al) is present in an amount of 55-99% by weight, preferably 60-95% by weight, and more preferably 60-85% by weight, based on the total weight of all the monomers (i.e., the one or more monomers) being used.
• the monomer of a2) is present in an amount of 1-50% by weight, preferably 5-40% by weight, and more preferably 5-30% by weight, based on the total weight of all the monomers (i.e., the one or more monomers) being used.
• the monomer of a3) is present in an amount of 0-20% by weight, preferably 0-16% by weight, more preferably 5-15% by weight, and most preferably 10-15% by weight, based on the total weight of all the monomers (i.e., the one or more monomers) being used.
• the monomer of a 1) is selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, hydroxymethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, or a mixture thereof.
• the monomer of a2) is glycidyl methacrylate.
• the monomer of a3) is methacrylamide, acryloyl morpholine, and/or methacrylic acid.
• the present invention also provides an electrically conductive adhesive composition, comprising the above-described thermally curable pressure-sensitive adhesive composition, and an electrically conductive material.
• the electrically conductive material includes but is not limited to metal particulates, alloy particulates, carbon black, graphene, electrically conductive minerals, electrically conductive organic compounds, surface-conductively -treated base materials, or a combination thereof.
• the base material that can be used for the present invention may be selected from fibers, small beads, thin slices, and other particulates with irregular shapes.
• the electrically conductive material is a surface- conductively-treated fiber (conductive fiber).
• the electrically conductive material is present in an amount of 10-90% by weight, preferably 30-70% by weight, and more preferably 40-60% by weight, based on the total weight of the composition.
• the electrically conductive adhesive comprises 10-90% by weight of the electrically conductive material and 10-90% by weight of the thermally curable pressure-sensitive adhesive composition, preferably 30-70% by weight of the electrically conductive material, and more preferably 40-60% by weight of the electrically conductive material and 40-60% by weight of the thermally curable pressure-sensitive adhesive composition, based on the total weight of the composition.
• the present invention also provides an adhesive tape comprising the above-described thermally curable pressure-sensitive adhesive composition, or the electrically conductive adhesive composition, and a base material.
• the present invention also relates to the use of the above-described thermally curable pressure- sensitive adhesive composition or the electrically conductive adhesive composition in preparing membranes used for electronic and electrical products, automobile products and new energy equipment.
• the thermally curable pressure-sensitive adhesive composition of the present invention is preferably cured at temperatures no higher than 220°C.
• curing temperature is 160-220°C, more preferably 170-190°C.
• the thermally curable pressure-sensitive adhesive composition of the present invention can be stored at 40°C, preferably at room temperature, for a long period of time, for as long as 8 months, and more preferably for more than 12 months.
• the reactive polymethacrylate component of the present invention is polymethacrylate having reactive functional groups.
• the reactive functional groups are epoxy group, carboxyl group and hydroxyl group, or a combination thereof.
• the reactive polymethacrylate component is present in an amount of 35-99% by weight, preferably 45-95% by weight, more preferably 55-95% by weight, even more preferably 60-95% by weight, and further more preferably 70-82% by weight, based on the total weight of the thermally curable pressure-sensitive adhesive composition.
• the reactive polymethacrylate component of the present invention is formed by free-radical polymerization of one or more monomers selected from the following monomers:
• a3) optionally, methacrylic acid and/or methacrylamide.
• the components of the composition can be so selected that the reactive polymethacrylate component not only has good compatibility with benzoxazine, but also reacts with benzoxazine at curing temperature during ring-opening of the benzoxazine when it is heated to form an interpenetrating polymer network (IPN) structure.
• IPN interpenetrating polymer network
• examples of the alkyl methacrylate in the component al) include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, isooctyl methacrylate, 2- ethylhexyl methacrylate, and the like, including possible isomeric forms thereof.
• the component al) alkyl methacrylate is selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, or a mixture of more than two types of the methacrylate in the group. More preferably, the component al) alkyl methacrylate is selected from the group consisting of butyl methacrylate, methyl methacrylate, isooctyl methacrylate, or a mixture of more than two types of the methacrylate in the group.
• examples of the alkyl methacrylate in the component al) include hydroxymethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, including possible isomeric forms thereof.
• the alkyl methacrylate in the component al include hydroxymethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, including possible isomeric forms thereof.
• the alkyl methacrylate in the component al) include hydroxymethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, including possible isomeric forms thereof.
• the methacrylate in the component al) is selected from the group consisting of hydroxymethyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, or a mixture of more than two types of the methacrylate in the group. More preferably, the alkyl methacrylate in the component al) is selected from the group consisting of hydroxymethyl methacrylate and/or hydroxyethyl methacrylate.
• the component al) preferably comprises both alkyl methacrylate and hydroxyalkyl methacrylate.
• the presence of hydroxyalkyl methacrylate is particularly favorable for achieving low curing temperature.
• examples of the alkyl methacrylate containing epoxy functional group in the component a2) include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, which contain a plurality of ternary or quaternary epoxyalkyl (epoxypropyl or epoxybutyl) units, and the like.
• the alkyl methacrylate containing epoxy functional group in the component a2) is the above-described methyl methacrylate substituted by epoxypropyl.
• the alkyl methacrylate containing epoxy functional group in the component a2) includes glycidyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether (4HBAGE), 3,4-epoxycyclohexyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, and the like.
• the alkyl methacrylate containing epoxy functional group in the component a2) includes glycidyl methacrylate.
• the monomer al) is present in an amount of 50-99% by weight, preferably 60-98% by weight, based on the total weight of all the monomers (i.e., the one or more monomers) being used.
• the monomer a2) is normally present in an amount of 2-70% by weight, and preferably 5-40% by weight, based on the total weight of all the monomers (i.e., the one or more monomers) being used.
• the inventors of the present invention have discovered that the monomer a2) with the amount in this range is favorable for aging resistance of the pressure-sensitive adhesive.
• the monomer a3) is present in an amount of 0-20% by weight, preferably 0-16% by weight, more preferably 5-15%, and most preferably 10-15%, based on the total weight of all the monomers (i.e., the one or more monomers) being used.
• the monomer a3) is optional. If present, the monomer a3) can be methacrylic acid, methacrylamide compounds or any mixtures thereof.
• the methacrylamide compounds that can be used for the present invention include
• methacrylamide such as N-tert-butyl acrylamide, N-hexyl methacrylamide, N-octyl acrylamide, N-nonyl methacrylamide, N-dodecyl methacrylamide, N-hexadecyl methacrylamide, N-methacrylamidocaproic acid, N-methacrylamidoundecanoic acid, ⁇ , ⁇ -dibutyl acrylamide, N-hydroxyethyl acrylamide, acryloyl morpholine and N-hydroxyethyl methacrylamide.
• the acryloyl morpholine is preferred.
• the inclusion of methacrylamide compounds is particularly favorable for achieving low curing temperature.
• the difference in solubility parameters should be taken into consideration; on the other hand, the reactive polymethacrylate component should be able to react with benzoxazine during ring-opening of the benzoxazine when it is heated to form an interpenetrating polymer network (IPN) structure.
• IPN interpenetrating polymer network
• the reactive polymethacrylate component of the present invention has a glass transition temperature (Tg) of -35°C to 32°C, preferably -25°C to 30°C, more preferably -22°C to 27°C, and most preferably -22°C to 10°C. Good strength of final adhesive can be achieved after being cured when Tg of the polymethacrylate component falls in this range.
• Tg glass transition temperature
• Tg of polymers can be measured by DSC and other conventional methods in the art, or can be calculated by the FOX equation.
• FOX equation see HE Manjun, et al. Polymer Physics (revised edition), Fudan University Press (Oct. 1990), p. 254.
• the FOX equation is an equation used for describing relationship of Tg of a copolymer with composition of the copolymer and with Tg of a homopolymer.
• Tg can be represented by the following equation:
• Tg is the Tg of copolymer
• W A , W B , W C and so on are mass fraction of monomer units A, B, C and so on, respectively;
• Tg A , Tg B , Tgc and so on are the corresponding Tg of homopolymer A, homopolymer B, homopolymer C and so on, respectively.
• the reactive polymethacrylate component a) of the present invention can be formed by free- radical polymerization of one or more monomers. Initiator, solvent and other auxiliary agents used for the polymerization are conventionally selected by those skilled in the art. These monomers should have good compatibility with benzoxazine. Monomers that can be used are as described above.
• the reactive polymethacrylate component a) having reactive functional groups as described above can be synthesized by conventional free-radical polymerization in solvent.
• the component a) is normally present in an amount of 35-99% by weight, preferably 45-95% by weight, more preferably 55- 95% by weight, even more preferably 60-95% by weight, and most preferably 70-82% by weight, based on the total weight of the thermally curable pressure-sensitive adhesive composition.
• the component can have good compatibility with benzoxazine and good toughness-enhancing effect on polybenzoxazine resin formed in the composition after being cured.
• Component b Benzoxazine
• Benzoxazine is another important component of the thermally curable pressure-sensitive adhesive composition used in the present invention. It can be any benzoxazine that can react during ring-opening when it is heated and has at least two oxazine functional groups.
• the benzoxazine used for the present invention has the following structure:
• Ci-Ce alkylene C3-C10 cycloalkylene
• Ri and R2 are the same or different and selected from the group consisting of hydrogen, Ci-Ce alkyl, or C5-Q4 aryl,
• R4 is selected from the group consisting of hydrogen, halogen or Ci-Ce alkyl.
• the above group Ri and R2 are selected from the group consisting of hydrogen, methyl, ethyl, propyl, butyl, phenyl, benzyl, and phenelethyl.
• examples of the benzoxazine include:
• the component b) benzoxazine is normally present in an amount of 1 -65% by weight, preferably 1-55% by weight, more preferably 1-50% by weight, even more preferably 5-40% by weight, and further more preferably 18-30% by weight, based on the total weight of the thermally curable pressure-sensitive adhesive composition. This will ensure the (semi-)structural adhesive tapes to have adequate strength after being cured.
• an electrically conductive adhesive composition comprising the thermally curable pressure-sensitive adhesive composition and an electrically conductive material.
• the electrically conductive material includes but is not limited to metal particulates, alloy particulates, carbon black, graphene, electrically conductive minerals, electrically conductive organic compounds, surface-conductively-treated base materials, or a combination thereof.
• the base material that can be used for the present invention may be selected from fibers, small beads, thin slices, and other particulates with irregular shapes.
• the electrically conductive functional component of the thermally curable pressure-sensitive adhesive composition referred to in the present invention can be electrically conductive fibers.
• Suitable electrically conductive fibers include practically any fiber materials that have a volume resistivity lower than about 50 microhm-cm ( ⁇ -cm), typically lower than about 4 ⁇ -cm.
• Examples of the electrically conductive fibers include fibers made of electrically conductive metals, such as copper, aluminum, silver and gold, and alloys thereof.
• the electrically conductive fibers can also be prepared by modification of electrical insulative materials, for example, by introducing a medium that provides electrical conductivity into a natural or synthetic polymer (e.g., incorporating metal particulates into fibers).
• the electrically conductive fibers can also be formed by electroplating or coating a metal on metallic fibers, or by electroplating a metal on non-metallic fiber cores.
• Metals used for electroplating on fibers include copper, nickel, cobalt, silver, gold, palladium, platinum, ruthenium and rhodium, and alloys thereof.
• Non-metallic fiber cores include carbon, graphite, glass, polyester, and other synthetic materials.
• Exemplary metal-electroplated fibers include nickel-electroplated carbon fibers, gold-coated polyethylene fibers, gold-electroplated polypropylene fibers, rhodium-coated fibers, copper fibers, silver fibers, aluminum fibers, and a combination thereof. A combination of the electrically conductive fibers may also be used.
• the electrically conductive metal is present in the electrically conductive fiber in an amount of 10-60% by weight, preferably 15-30% by weight, and more preferably 15-25% by weight.
• the ratio of length to diameter of the electrically conductive fiber is about 2-20, preferably 5-15.
• average length of the electrically conductive fiber can be 50-500 microns, preferably 60-300 microns, and more preferably 75-150 microns.
• Commercial electrically conductive fibers such as, for example, SF82TF20 of Potters Industries Inc., Valley Forge, Pennsylvania, has a silver content of 20% by weight and average length x diameter of 130 x 15 microns.
• the electrically conductive material is normally in an amount of 10-90% by weight, preferably 30-70% by weight, more preferably 40-60% by weight, based on the total weight of the electrically conductive adhesive composition. However, more or less amount can also be used. More specifically, the electrically conductive adhesive comprises 10-90% by weight of the electrically conductive material and 10-90% by weight of the thermally curable pressure-sensitive adhesive composition, preferably 30-70% by weight of the electrically conductive material, and more preferably 40-60% by weight of the electrically conductive material and 40-60% by weight of the thermally curable pressure-sensitive adhesive composition, based on the total weight of the electrically conductive adhesive composition. The amount of the reactive polymethacrylate component and benzoxiazine component is consistent with what is described above for the thermally curable pressure-sensitive adhesive composition. iv. Membrane preparation
• the thermally curable pressure-sensitive adhesive composition and corresponding electrically conductive adhesive composition of the present invention may be coated on a base material to form a membrane.
• the base material may include, for example, single-sided release paper or release film.
• compositions can be coated in a liquid form on a base material having a certain thickness with a conventional method, and then solvent is removed by heating to form an adhesive membrane having a certain thickness.
• thermally curable, high-temperature resistant, pressure-sensitive semi-structural adhesive of the present invention should have a viscosity between 500 and 23000 cP, preferably between 1500 and 16000 cP, before being coated. Either extraordinarily high or extraordinarily low viscosities are unfavorable for coating of the thermally curable pressure-sensitive adhesive.
• (semi-)structural adhesive membrane may be between 8 and 250 microns, preferably between 25 and 150 microns, more preferably between 50 and 125 microns. Either extraordinarily high or extraordinarily low viscosities are unfavorable for coating of the thermally curable pressure-sensitive adhesive. Either extraordinarily large or extraordinarily small thicknesses are unfavorable for coating and use of the thermally curable pressure-sensitive adhesive. v. Advantageous results of the present invention
• composition adhesive tape made thereof has the following advantages: having initial adhesion and die-cutting mouldability of pressure-sensitive adhesives;
• the thermally curable, high-temperature resistant, pressure-sensitive (semi-)structural adhesive of the present invention demonstrates characteristics of conventional pressure-sensitive adhesive tapes (i.e., having initial adhesion, being able to adhered to an object upon application of minimal pressure, being able to be formed by die-cutting); and can be cured at a certain temperature, and can achieve semi- structural to structural strength after being cured.
• Cured adhesive tapes have high temperature resistance (150°C for long term, 280°C for short term, as reflow soldering process) and long-term aging-resistance. Therefore, they are particularly suitable for applications in electronic and electric, automobile and new energy (solar energy and wind energy) markets.
• Another advantage of the present invention is that such thermally curable, high-temperature resistant, semi-structural adhesives and adhesive tapes made thereof according to the present invention can be stored at room temperature for such a long time (as long as over 12 months at room temperature) that transportation and storage costs for the thermally curable, high-temperature resistant, semi-structural adhesives and adhesive tapes made thereof manufactured according to the present invention can be dramatically reduced.
• benzoxazine and polymethacrylate components in the composition of the present invention produce a synergistic effect, which not only provides good temperature -resistance and (semi-)structural strength, but also significantly reduces brittleness of benzoxazine resin, and effectively reduces curing temperature of the system, and provides good film- forming ability for producing adhesive membranes or adhesive tape products.
• the thermally curable, high-temperature resistant, pressure-sensitive (semi-)structural adhesives and adhesive tapes made thereof can achieve (semi-)structural strength after being thermally cured, in addition to preserving advantages of convenience and effectiveness in the use of ordinary pressure-sensitive adhesive tapes.
• the thermally curable pressure-sensitive adhesive composition of the present invention comprises a hybrid system of reactive polymethacrylate and benzoxazine resin.
• the thermally curable pressure-sensitive semi-structural adhesive composition may be incompletely cured when being cured. However, it has already achieved semi-structural strength and can fully meet requirement for the use although incompletely cured. Since the special reactive polymethacrylate is reactive and able to form an interpenetrating polymer network (IPN) with benzoxazine, the system can withstand higher temperatures. Meanwhile, such thermally curable, high-temperature resistant (semi-)structural adhesives and adhesive tapes made thereof can be stored at room temperature for as long as over 12 months. Since benzoxazine resin does not release small molecules and has nearly zero shrinkage when being further cured, it will not affect applications.
• the high temperature resistance of the pressure-sensitive adhesive composition of the present invention allows the composition to be used in various fields where demanding requirements are imposed for temperature resistance.
• reflow soldering process is used for assembly of hybrid circuit board because of requirement for miniaturization of electronic PCB products.
• a majority of fabricators have already adopted a lead- free reflow soldering process in order to care more about environment protection.
• the process temperature can reach 260°C for several minutes (even 300°C for 5 minutes for testing purpose). Under such conditions, the adhesives or adhesive tapes must not be degraded and can maintain sufficiently high bond strength to ensure reliability of bonded parts.
• solar cell assembly would have economic values to be commercialized only when they can achieve an outdoor service life of at least 25 years. Therefore, solar cell assembly is generally required to pass the following accelerated ageing test: thermal cycling test (-40°C to 90°C), 200 cycles (TC200); damp heat test (85°C/85% RH), 1000 hours (DH1000), and low temperature test (HF10). All these tests require bonding agents to have good temperature resistant properties.
• the thermally curable, high-temperature resistant, pressure-sensitive semi-structural adhesive tape of the present invention is separated from its release paper, and is adhered to a standard testing aluminum plate with its adhesive surface, and then covered with another standard testing aluminum plate.
• the two standard testing aluminum plates are clamped together with an iron clamp and placed into an oven for curing at a certain temperature, and then placed in an environment of constant temperature 23°C and constant humidity of 50% for 24 hours before being tested.
• test is performed in accordance with the methods described in FINAT FTM 2 (FINAT Technical Handbook - Test Methods, 8 th edition), and shear strength can be directly determined.
• the electrically conductive adhesive tape is cut into 25-mm-wide specimen strips.
• the adhesive surface of the adhesive tape is adhered to a 25-micron polyimide (PI) film or a 5-mil anodized aluminum foil, and thermally pressed at 180°C and 0.4 MPa for 10 seconds (sec).
• the release paper or release film on the back of the adhesive tape is peeled off, and the PI film or aluminum foil with the adhered adhesive tape is placed on another PI film or aluminum foil with the adhesive surface facing the film or foil, and then thermally pressed at 180°C and 0.4 MPa for 30 minutes (min).
• the laminated test strip is placed into an oven of 180°C and heated for 30 min before being cooled at room temperature for over 1 hour.
• test is performed in accordance with the methods described in FINAT FTM 2 (FINAT Technical Handbook - Test Methods, 8 th edition), and T-type peel strength can be directly obtained. All the tests are performed with the 25-micron polyimide (PI) film as a base material.
• PI polyimide
• Preservation at room temperature is evaluated by determining changes in OLS.
• initial OLS, P0 of newly made adhesive tapes is determined, and the adhesive tapes are kept in an oven at a certain temperature (40°C) for a period of time before the OLS, PI, is determined again with the same method. If PI can be maintained at 80% of P0, preservation period is deemed to be the longest.
• Curing degree can be conveniently determined with DCS (TA Q200) since curing reaction is generally an exothermic reaction.
• the amount of released heat depends on the type of functional groups of the resin, the number of the functional groups involved in the reaction, and the type and amount of curing agent. However, for a resin system of a certain formulation, the released heat of the curing reaction is definite. Therefore, the curing degree a can be calculated with the following equation:
• ⁇ 0 is the total amount of heat released (J/g) when the incompletely cured resin system is completely cured
• AHR is the residual reaction heat (J/g) after curing.
• Thermal stability can be characterized by using thermogravimetric analysis (TA Q500) with an air flow of 60 mL/min and a heating rate of 10°C/min.
• TA Q500 thermogravimetric analysis
• a specimen is cured under certain conditions and then placed into an aging oven at 85°C and
• OLS is determined in accordance with the methods described in Test Method 2.
• the electrically conductive adhesive tape is cut into 18 mm x 18 mm specimens.
• the adhesive surface of the adhesive tape is adhered to a SUS316L stainless steel strap ( ⁇ 15.5 mm in diameter, 0.5 mm in thickness), and thermally pressed at 180°C and 0.4 MPa for 10 sec.
• the release paper or release film on the back of the adhesive tape is peeled off, and the stainless steel strap with the adhered adhesive tape is placed in a copper-exposed area on a test plate, with the adhesive surface facing the copper-exposed area, and then thermally pressed at 180°C and 0.4 MPa for 30 min.
• the laminated test plate and the stainless steel strap is placed into an oven of 180°C and heated for 30 min before being cooled at room temperature for over 1 hour.
• the adhesive tape was cured at 180C for 30 min according to the test method 1, and then its
• OLS was determined according to the test method 2.
• the OLS values after aging are more related to the GMA contents.
• the OLS values after aging would be reduced if the polymer contains no GMA.
• aging resistance can be significantly increased once the polymer contains more than 5% of GMA. That is because the epoxy functional group in GMA monomer can react with benzoxazine resin to yield an interpenetrating polymer network (IPN) structure.
• IPN interpenetrating polymer network
• a thermally curable, high-temperature resistant, pressure-sensitive semi-structural adhesive tape can be obtained after it was dried to remove solvent in an oven at 105°C for 10 min.
• the adhesive tape was cured at 180°C for 30 min according to the test method 1, and then its OLS was determined according to the test method 2.
• the reactive polymethacrylate RPABOZ-8 to RPABOZ-16 have the same GMA content (5%), but different Tg (from -63°C to 27°C).
• Tg of the reactive polymethacrylate is too low ( ⁇ -60°C)
• its OLS values are also extremely low, and the reactive polymethacrylate essentially have no semi-structural strength.
• Tg of the reactive polymethacrylate is increased, its OLS is also increased.
• Tg reaches 10°C or above the increase of OLS becomes unobvious, but brittleness of the adhesive will be increased.
• a thermally curable, high-temperature resistant, pressure-sensitive semi-structural adhesive tape can be obtained after it was dried to remove solvent in an oven.
• the adhesive tape was cured at 180°C for 30 min according to the test method 1 , and then its OLS (MPa) was determined according to the test method 2, and its T-type peel strength (N/mm) was determined according to the test method 3.
• Table 7 :
• the OLS of the adhesive after aging at high temperatures can still reach 1.64 MPa.
• the OLS exhibits a tendency of increase at first and decrease afterwards. This is mainly because the conditions of curing at 180°C for 30 min are not sufficient for all the benzoxazine to be completely cured. The extra benzoxazine monomers will cause OLS to decrease on the contrary. Also, the peel strength has the similar tendency. It can be seen that as long as the ratio between the reactive polymethacrylate and benzoxazine is properly matched, a formulation with relatively balanced shear force and peel force can be obtained.
• a thermally curable, high-temperature resistant, pressure-sensitive semi-structural adhesive tape can be obtained after it was dried to remove solvent in an oven.
• the adhesive tape was cured at 180°C for 30 min according to the test method 1 , and then its OLS (MPa) was determined according to the test method 2, and its T-type peel strength (N/mm) was determined according to the test method 3.
• Table 8 :
• the reactive polymethacrylate RPABOZ-24 contains hydroxyl (-OH) and epoxy groups
• the reactive polymethacrylate RPABOZ-25 contains acrylic acid (AA) and amido groups. It is found that their OLS values are close to the results of the reactive polymethacrylate of RPA-C series having corresponding Tg. However, their initial reaction temperature will be slightly different. See evaluation of curing properties of reactive polymethacrylate/ benzoxazine systems for details.
• Test Example 5 Evaluation of aging properties of the reactive polymethacrylate/benzoxazine systems
• test Example 6 Evaluation of curing properties of the reactive polymethacrylate/benzoxazine systems Four specimens as indicated in Table 10 were cured at 150°C for 30 min, at 180°C for 30 min and at 210°C for 30 min according to the test method 1, respectively, and then their OLS (MPa) was determined according to the test method 2, and their curing extent was evaluated according to the test method 5.
• Figure 1 shows rheological curves of elastic modulus (G') (by ARES Rheometer of TA
• Test Example 8 Evaluation of storage properties of the reactive polymethacrylate/benzoxazine systems at room temperature
• Z-axis conductivity is achieved by adding electrically conductive fibers while high viscosity is still maintained.

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